Drawing a graph that updates in realtime based on input using Java?

Question

So I have little experience with graphical drawing in java so my first question is essentially: what tutorials shall I view in order to draw a graph in java?

The second question is my main task. I would like to be able to draw a graph in java that is updating in realtime (or every 10 seconds) with new data taken from a file i.e: I will pipe a file to the program and every so often it will check the file for new data, and update the visual graph with the new data, but this has to be in real time meaning the graph keeps all previous data already drawn and will be seen to be moving left to right (upon the reaching the edge of the screen the X-axis will then start moving left with higher numbers.

Are there any already written algorithms that do this? or if I have to accomplish this myself could anyone give me a pointer on where to begin?

Thanks,

Euden

Community · Accepted Answer · 2017-05-23 12:30:21Z

3

Why not use JFreeChart ? It's a widely used charting library. It claims not to be suitable for realtime use, but for the frequencies you're talking about (every 10s) it should be perfectly suitable.

This answer links to some example code.

edited May 23, 2017 at 12:30

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answered Oct 2, 2012 at 16:57

Brian Agnew

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1 Comment

Ben Crazed Up Euden Over a year ago

JFreeChart was perfect for my needs. Thank you!

onebeartoe · Accepted Answer · 2012-10-02 19:31:26Z

If you can use Java 7, then check out the JavaFX APIs. There is a stock ticker that comes with Oracle's Ensemble samples (chart -> lines -> advanced stock). It is a good start for what you are trying to achieve. Here is the code provided by Oracle:

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.animation.Animation;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.util.Duration;

/**
 * A simulated stock line chart.
 *
 * @see javafx.scene.chart.Chart
 * @see javafx.scene.chart.LineChart
 * @see javafx.scene.chart.NumberAxis
 * @see javafx.scene.chart.XYChart
 */
public class AdvancedStockLineChartSample extends Application {

    private XYChart.Series<Number,Number> hourDataSeries;
    private XYChart.Series<Number,Number> minuteDataSeries;
    private NumberAxis xAxis;
    private Timeline animation;

    private double hours = 0;
    private double minutes = 0;
    private double timeInHours = 0;
    private double prevY = 10;
    private double y = 10;

    private void init(Stage primaryStage) {
        Group root = new Group();
        primaryStage.setScene(new Scene(root));
        root.getChildren().add(createChart());
        // create timeline to add new data every 60th of second
        animation = new Timeline();
        animation.getKeyFrames().add(new KeyFrame(Duration.millis(1000/60), new EventHandler<ActionEvent>() {
            @Override public void handle(ActionEvent actionEvent) {
                // 6 minutes data per frame
                for(int count=0; count < 6; count++) {
                    nextTime();
                    plotTime();
                }
            }
        }));
        animation.setCycleCount(Animation.INDEFINITE);
    }

    protected LineChart<Number, Number> createChart() {
        xAxis = new NumberAxis(0,24,3);
        final NumberAxis yAxis = new NumberAxis(0,100,10);
        final LineChart<Number,Number> lc = new LineChart<Number,Number>(xAxis,yAxis);
        // setup chart
        lc.setId("lineStockDemo");
        lc.setCreateSymbols(false);
        lc.setAnimated(false);
        lc.setLegendVisible(false);
        lc.setTitle("ACME Company Stock");
        xAxis.setLabel("Time");
        xAxis.setForceZeroInRange(false);
        yAxis.setLabel("Share Price");
        yAxis.setTickLabelFormatter(new NumberAxis.DefaultFormatter(yAxis,"$",null));
        // add starting data
        hourDataSeries = new XYChart.Series<Number,Number>();
        hourDataSeries.setName("Hourly Data");
        minuteDataSeries = new XYChart.Series<Number,Number>();
        minuteDataSeries.setName("Minute Data");
        // create some starting data
        hourDataSeries.getData().add(new XYChart.Data<Number,Number>(timeInHours,prevY));
        minuteDataSeries.getData().add(new XYChart.Data<Number,Number>(timeInHours,prevY));
        for (double m=0; m<(60); m++) {
            nextTime();
            plotTime();
        }
        lc.getData().add(minuteDataSeries);
        lc.getData().add(hourDataSeries);
        return lc;
    }

    private void nextTime() {
        if (minutes == 59) {
            hours ++;
            minutes = 0;
        } else {
            minutes ++;
        }
        timeInHours = hours + ((1d/60d)*minutes);
    }

    private void plotTime() {
        if ((timeInHours % 1) == 0) {
            // change of hour
            double oldY = y;
            y = prevY - 10 + (Math.random()*20);
            prevY = oldY;
            while (y < 10 || y > 90) y = y - 10 + (Math.random()*20);
            hourDataSeries.getData().add(new XYChart.Data<Number, Number>(timeInHours, prevY));
            // after 25hours delete old data
            if (timeInHours > 25) hourDataSeries.getData().remove(0);
            // every hour after 24 move range 1 hour
            if (timeInHours > 24) {
                xAxis.setLowerBound(xAxis.getLowerBound()+1);
                xAxis.setUpperBound(xAxis.getUpperBound()+1);
            }
        }
        double min = (timeInHours % 1);
        double randomPickVariance = Math.random();
        if (randomPickVariance < 0.3) {
            double minY = prevY + ((y-prevY) * min) - 4 + (Math.random()*8);
            minuteDataSeries.getData().add(new XYChart.Data<Number,Number>(timeInHours,minY));
        } else if (randomPickVariance < 0.7) {
            double minY = prevY + ((y-prevY) * min) - 6 + (Math.random()*12);
            minuteDataSeries.getData().add(new XYChart.Data<Number,Number>(timeInHours,minY));
        } else if (randomPickVariance < 0.95) {
            double minY = prevY + ((y-prevY) * min) - 10 + (Math.random()*20);
            minuteDataSeries.getData().add(new XYChart.Data<Number,Number>(timeInHours,minY));
        } else {
            double minY = prevY + ((y-prevY) * min) - 15 + (Math.random()*30);
            minuteDataSeries.getData().add(new XYChart.Data<Number,Number>(timeInHours,minY));
        }
        // after 25hours delete old data
        if (timeInHours > 25) minuteDataSeries.getData().remove(0);
    }

   public void play() {
        animation.play();
    }

    @Override public void stop() {
        animation.pause();
    }    

    @Override public void start(Stage primaryStage) throws Exception {
        init(primaryStage);
        primaryStage.show();
        play();
    }
    public static void main(String[] args) { launch(args); }
}

Screen shot: enter image description here

I was unaware of JavaFX. Although I used JFreeChart, this is useful. Thank you.

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